Method of electrical brazing of conductors



G. E- BERGG REM METHOD OF ELECTRICAL BRAZING OF CONDUCTORS Filed Nov.10, 1944 Jan. 25, 1949.

2 Sheets-Sheet l lNVENTOE G. E. BERGGREN ATTORNEY Jan. 25, 1949. e. E.BERG'GRE'N 2,459,863

METHOD OF ELECTRICAL BRAZING OF CONDUCTORS Filed Nov. 10, 1944 2Sheets-Sheet 2 lNVE/VTOI? G. E. BE R6 GRE N A TTORNEV Patented Jan. 25,1949 METHOD OF ELECTRICAL BRAZING OF CONDUCTORS George E. Berggren,Baltimore, Md., assignor to Western Electric Company, Incorporated, NewYork, N. Y., a corporation of New York Application November 10, 1944,Serial No. 562,848

2 Claims. 1

This invention relates to methods of brazing articles, and moreparticularly to methods of brazing electrical conductors.

In the manufacture of electrical conductors, it is often necessary tosplice the conductors by brazing. To obtain strong splices by brazing,the brazing material must be heated to a high temperature, but theconductors should not be heated to a temperature which would cause themto become brittle or be fully annealed if they are tempered. Also, ifthe conductors are heated to a very high temperature during the brazingthereof, they oxidize, and if insulating jackets are on the conductors,there is danger of melting or burning the portions of the insulatingjacket thereon adjacent to the portions of the conductors being brazed.

In brazing conductors with silver solder, it is necessary that thesilver solder be heated at a relatively high temperature until it ismolten. It is desirable to heat the portions of the conductors to bebrazed to a temperature sufiiciently high to form a good joint, but tolimit the temperature of these portions so that the strength of theconductors will not be altered materially, and the adjacent portions ofthe conductors will not be heated sufficiently to damage any insulatingjackets thereon.

An object of the invention is to provide. new and improved methods ofbrazing articles.

One method embodying the invention comprises positioning a mass ofbrazing material between two metal articles to be brazed together,heating the mass of brazing material to a brazing temperature, and thenheating the portions of the articles adjacent to the heated mass ofbrazing material to a brazing temperature.

A complete understanding of the invention may be obtained from thefollowing detailed description of a method forming one embodimentthereof, when read in conjunction with the appended drawings, in which:

Fig. l is a vertical, sectional view of an apparatus suitable for use inpracticing a method of embodying the invention;

Fig. 2 is an enlarged, fragmentary, horizontal sectional view of aportion of the apparatus taken along line 22 of Fig. 1;

Fig. 3 is a fragmentary, horizontal sectional view of a portion of theapparatus taken along line 33 of Fig. 1;

Fig. 4 is an enlarged, fragmentary, vertical sectional view of a portionof the apparatus taken along line 4-4 of Fig. l, and showing one stagein a brazing operation;

Fig. 5 is a view similar to Fig. 4 showing another stage in a brazingoperation;

Fig. 6 is another view similar to Fig. 4 showing still another stage ina brazing operation;

Fig. 7 is an enlarged, fragmentary, exploded, perspective view of a pairof electrodes forming apart of the apparatus;

Fig. 8 is an enlargedperspective view of a disc of brazing material tobe used in a method embodying the invention, and

Fig. 9 is a diagrammatic view of an electric circuit comprising a partof the apparatus.

Referring more in detail to the drawings, there is shown therein anapparatus for performing a method of brazing embodying the invention.This apparatus is designed to splice together the ends of insulated oruninsulated conductors, which may be solid or stranded. For purposes ofillustration, there is described hereinbelow the method of brazingstranded conductors l2 and I3 having insulating jackets l4 and 15,respectively, thereon.

A stationary .carbon electrode 20 (Fi'gs.f1 and 7) having a plurality ofarcuate grooves 2l'2l formed therein is connected by a conductor. 22 toa secondary winding 23 (Fig. 9) of a transformer 24, and a conductor25.connects a'movable car.- bon electrode 26 to the secondary winding23. of the transformer 24. A fixed electrode holder 30 (Fig. 1) servesto mount the carbon" electrode 2}] rigidly, and an electrode holderl 3ifixed to an arm 32 serves to mount the carbon electrode 25 on the arm.The arm 32 is pivotally attached at one end thereof to a bracket 33 andis provided with a handle 34 at the free end thereof. A manuallyoperable, spring-pressed latch 35 (Figs. 1 and 3) mounted on the armcooperates with a stop 36 to maintain the arm in its dotted lineposition, as shown in Fig. 1, when the apparatus is not in use. Thelatch may be released and the arm pivoted in a counterclockwisedirection, as viewed in Fig. 1, when desired. The weight of the arm andthe electrode '26 move the electrode 26 toward the electrode 20 when thelatch is released.

A wire trimmer 40 (Figs. 1 and 2) includes a supporting plate, 4| havingfixed thereto a disc 42, which is provided with bores 4343 therein. Adisc 44 having a handle 45 formed thereon is mounted pivotally above thedisc 42 by a bolt 46, and has formed therein bores 50, which may bealigned with the bores 43--43, which are just large enough to receivethe; conductors l2 and I3 therein. To trim the ends ofthe-conductors l23 and I 3 (Fig. 4), the disc (Fig. 2) is moved to a position in whichthe bores 5IJ-5fi are aligned with the bores 4343, the conductor I2 isinserted into a pair of the aligned bores and the disc is rotatedrelative to the disc 42, whereby the portion of the conductor l2projecting into the bored-Sis severed neatly from the portion of theconductor positioned in the .oorebfl. This "operation is repeated withthe conductor l3. After the ends of the conductors l2 and 13 have beentrimmed, the ends are clean and are hat and perpendicular to the axes ofthe conductors so that they will form a tight and short splice;

A constant voltage power line 5i (Fig 9) serves to supply current to anelectronic timer 5?. of standard construction, which is connected byconductors 53-53 to a primary winding 5d of .the transformer 26., andhas a manually operable,

normally open, push-button switch 55 therein.

When the push-button "switch 55 is closed, the timer52 and the primarywinding 5% of the transformer v are energized, whereby the secondarywinding 23 of the transformer is energized and a potential is impressedupon the electrodes .23 and-2B. After the switch 55 has been closed .iora short, predetermined period of time, the timer 52 serves to break thecircuit to the transtormer- .24. whereby the electrodes 20 and 26receive nomore power.

A spring-pressed clampfio positioned adjacent to the electrode 20 servesto hold the conductor 12 in the position shown in Fig. 4 .of thedrawings, in which position'the end of the conductor 12 restsin .oneofthe grooves 2l-2l in the electrode .20. A disc SI of silver solder alsois positioneddn the groove 2| so that one face thereof abuts theitrimmed end of the conductor l2. The disc, which is of a predeterminedsize, has a diameter slightly greater than the diameter of theconductors Wand l3, and therefore projects somewhat above "the conductorl2 resting in the groove 2i.

To braze the ends of the conductors I2 and i3 (Fig. 4) together, theyaretrimmed by means of the wire trimmer "413 (Fig. 2), and the conductor T2(Fig. '4) 'is clamped in the clamp "68 with the trimmed end thereof"extending about half way throughone of the grooves 21 2i "formed'in theelectrode 20. The disc'tfil of silver solder then is pressed against theend or the conductor i2 and -theconductor f3 isplace'd'in the positionshown Ein- Fig. J4 oi the drawings, in which position the fhd. "of "the"trimmed conductor l3 rests in the ,sgroojve 2| containing 'thedisc t!and abuts the The operator presses the conductor core disc.

l3 toward the disc "6! and the core :2 and maintains this pressure. Atthis time, theconductor-s IZan'd 1'3 lie in theb'ottom or the groove 2%and the disc 311, which is slightly larger in diameter than theconductor cores, projects slightly above the upper portions of theconductor cores somewhat inthe manner shown in Fig. 4.

The latch- 35 (Fig. '11 then is released and the arm '32 and theelectrode 26 are moved downwardly until the electrode 26 "engages theupper surface of the disc 5| (Fig. 4), which holds the electrode zs outof contact with the conductors l2 and '13. 'The'push-button switch "55(Figs. 1 and 9) then is'closed, whereby current is :sup-:plied'tothe-electrodes as (Fig. '4) and 'ii hows through the "disc iii.:Since the elect-rode 25 does not contact the conductors i 2 and 13,current does not flow through *the conductors "at this time. The current:flowing through the :tiisc 6! znelts theidiso and the conductor 13,whi-chis pressed against the disc 6!, moves toward the conductor I2 asthe disc 6% melts.

As the disc it melts, the molten solder flows around the end portions ofthe conductors i2 and 5 i3 and into the interstices between the strandsthereof, and the Weight of the arm 32 and. the

electrode 26 moves the electrode into engagement with the conductors i2and i3, as shown in Figs. 5 and 6. Current then LOWS through the adportions of the conductors 5?. and 53, wherey the end portions of theconductors are heated for a short period of time to provide good bondsbetween them and the melted disc. The timer iz then. breaks the circuitto the electrodes.

Thetimer 52 (Fig. 9) is set so that the disc '64 (Fig. 5) will be ieltedand the electrode 26 will contact the conductors i2 and only for aperiod of time suihcient to heat the is of the conductors i2 and it to atemperature high enough to make rigid bonds between the conductors andthe silver solder or the disc til without heating the conductors i2 andis to such an extent that the temper thereof will be destroyed or theinsulating covers i l and iii are burned'by 7 the heat of theconductors.

lnpracticing a specific method embodying the invention to brace strandedconductors of a diameter of .6456 inch, a disc or" silver solder of athickness of .0015 inch and a diameter of .0625 inch is verysatisfactory. The period of time in. which current is supplied to theelectrodes for brazing such conductors is slightly less than /2 of onesecond and the electrodes are subjected to a potential difierence ofabout 5- volts. The above-described values should be varied suitably forbrazing conductors of different sizes.

As the disc 5! (Fig. 5) is melted and the conductor 13 is pressed towardthe conductor 12, the conductor is is moved toward the conductor 12 anda very short, stiif splice section. will be formed. The silver solderflows around the ends of the :conductor cores, but is of such smallquantity that the resultant joint is very little larger than theconductors.

By practicing the above-described method of brazing conductors, veryneat and strong brazed joints may be formed without injuring either theconductors or the insulating jackets surrounding the conductors. At thesame time the joints are of substantially the same diameter as 3.6 con-'du'ctors themselves.

What is 'claime'd'is:

, 1. The method of brazing stranded electrical conductors ofpredetermined shape, which comprises clamping a stranded electricalconductor 'in contact with the bottom of a groove formed in an electrodeand having the shape of the con- 'ductor, pressing a preformed disc ofbrazing material of a diameter greater than that of the c0nducto'r and apredetermined mass in the groove against the end of the conductor,holding the end of a second stranded conductor against the opposite'side of the disc and in contact with the :bottom of the groove.pressing a second electrode against the periphery of the preformed discwith a predetermined amount of pressure, and passing a predeterminedamount of current from one of the electrodes to the other electrode fora predetermined period of time, wherebythe current initially flowsthrough only the disc of brazing material and melts the brazingmaterial, the second electrode moves into contact withthe 'end portionsof the conductors as the brazing material melts and flows into the 5interstices between the strands of the conductors,

and a current flows through the ends of the conductors after the secondelectrode has moved into an engagement therewith, whereby a brazed jointis formed of the same diameter as that of the stranded conductors.

2. The method of brazing stranded electrical conductors of predeterminedcontour, which comprises clamping a stranded electrical conductor incontact with the bottom of a groove formed in a fixed electrode andhaving the contour of the conductors, pressing a preformed slug ofbrazing material having a cross sectional area greater than that of theconductor and of a predetermined mass against the end of the conductor,holding the end of a second stranded electrical conductor against theopposite side of the slug and in contact with the electrode, pressing asecond electrode against the periphery of the preformed slug with apredetermined amount of pressure, and passing a predetermined amount ofcurrent from one electrode to the other electrode for a predeterminedperiod of time, whereby the current sequentially flows through the slugREFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 396,015 Thomson Jan. 8, 18891,040,418 Reitzel Oct. 8, 1912 1,332,670 Lachman Mar. 2, 1920 1,640,798Murray Aug. 30, 1927 OTHER REFERENCES Welding Handbook, 1942, pages 392,395 and 396 (American Welding Society, 33 West 39th Street, New York,New York.

Certificate of Correction Patent No. 2,459,863. January 25, 1949.

GEORGE E. BERGGREN It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows:

Column 4, line 60, claim 1, for the Words and a read and of a;

and that the said Letters Patent should be read With this correctiontherein that the same may conform to the record of the case in thePatent Oflice.

Signed and sealed this 1st day of November, A. D. 1949.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents.

' Certificate of Correction v PatentiY l. I 2 ;f$9, 63. J weary-25, 19

' GEORGE E. BERGGREN It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows:

Column 4, line 60, claim 1, for the Words and a read and of a;

and that the said Letters Patent should be read with this correctiontherein that the same may conform to the record of the case in thePatent Oflice.

Signed and sealed this 1st day of November, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

